Question

I am trying to open this file in java and i want to know what i am doing wrong. The in file lies in the same directory as my Java file, but i tried to open this with both netbeans and eclipse and it gave a file not found exception. Can someone help me open this file and read from it. I am really new to java files. Here is the code

 import java.util.*;
    import java.io.*;

    public class Practice
    {

      public static void main(String[] args)throws IOException
      {


          FileReader fin = new FileReader("anagrams.in");
          BufferedReader br = new BufferedReader(fin);



          System.out.println(fin);


        String string = "Madam Curie";
        String test = "Radium came";

        string = string.toLowerCase();
        test = test.toLowerCase();

        string = string.replaceAll("[^a-zA-Z0-9]+", "");
        test = test.replaceAll("[^a-zA-Z0-9]+", "");

        char[] array = string.toCharArray();
        char[] array2 = test.toCharArray();

        boolean flag = false;
        HashMap hm = new HashMap();


        for(int i = 0; i < array.length; i++)
        {
            hm.put(array[i], array[i]);
        }

       for(int i = 0; i < array2.length; i++)
       {
           if(hm.get(array2[i]) == null || test.length() != string.length())
           {
               flag = false;
               i = array2.length;
           }
           else
           {
               flag = true;
           }

       }

       System.out.println(flag);
      }

    }

Answer 1

A few tips:

1. Abide to proper code indentation
   • If you’re using an IDE like Eclipse, it can automatically correct indentation for you
2. Develop debugging instinct
   • Try to get what the current working directory is, and list all the files in it
3. Refactor repetitive code
   • Writing paired statements like you did should immediately raise red flags
4. Effective Java 2nd Edition
   • Item 23: Don’t use raw types in new code
   • Item 52: Refer to objects by their interfaces
   • Item 46: Prefer for-each loops to traditional for loops
5. Use sensible variable names

With regards to 2, try something like this:

public static void listDir() {
    File current = new File(".");
    System.out.println(current.getAbsolutePath());
    for (String filename : current.list()) {
        System.out.println(filename);
    }
}

Then in your main, simply call listDir before everything else, and see if you’re running the app from the right directory, and if there’s a "anagrams.in" in the directory. Note that some platforms are case-sensitive.

With regards to 3 and 4, consider having a helper method like this:

static Set<Character> usedCharactersIn(String s) {
    Set<Character> set = new HashSet<Character>();
    for (char ch : s.toLowerCase().toCharArray()) {
        set.add(ch);
    }
    return set;
}

Note how Set<E> is used instead of Map<K,V>. Looking at the rest of the code, you didn’t seem to actually need a mapping, but rather a set of some sort (but more on that later).

You can then have something like this in main, which makes the logic very readable:

    String s1 = ...;
    String s2 = ...;

    boolean isNotQuiteAnagram = (s1.length() == s2.length()) &&
        usedCharactersIn(s1).containsAll(usedCharactersIn(s2));

Note how variables are now named rather sensibly, highlighting their roles. Note also that this logic does not quite determine that s1 is an anagram of s2 (consider e.g. "abb" and "aab"), but this is in fact what you were doing.

Since this looks like homework, I’ll leave it up to you to try to figure out when two strings are anagrams.

See also

• Java Coding Conventions
• Java Language Guide/For-each loop
• Java Tutorials/Collections Framework

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